Severe acute respiratory syndrome (SARS) emerged as a new human infection in South China in 2002, and ultimately caused over 8,000 infections and almost 800 deaths as it spread to five continents along airline routes. While the overall mortality rate from SARS during the 2002-03 pandemic was approximately 10 percent, the mortality among the elderly exceeded 50 percent. Subsequent outbreaks were reported later in 2003 with the latest outbreak in 2004 in China occurring as a result of accidental exposure in a laboratory.

SARS outbreaks remain a serious global concern because of the continued threat of transmission from animals to humans or the accidental or intentional release of virus stored in laboratories. The prospect of renewed transmission of SARS to human populations suggests an urgent need to prepare vaccines for this emerging infectious agent. Vaccines to protect high-risk groups, including the elderly, healthcare workers and laboratory personnel, are particularly critical.